Does my American Bulldog puppy weigh enough?

I have a just about 12 week old American bulldog puppy. She is 20 pounds but very tall it's almost like she is growing up and not filling out much. You can see her ribs but she has a belly and lots of muscle. I'm feeding her by her weight chart 3 times a day. I'm just wondering if this is a normal weight. Her parents were 95 and 115 pounds and she came from a big litter (14)